Practice Questions

Q24.A thin rod having a length of 1 m and area of cross-section 3 × 10-6 m2 is suspended vertically from one end. The rod is cooled from 210°C to 160°C. After cooling, a mass 𝑀 is attached at the lower end of the rod such that the length of rod again becomes 1 m. Young's modulus and coefficient of linear expansion of the rod are 2 × 1011 N m-2 and 2 × 10-5 K-1, respectively. The value of 𝑀 is ______ kg. (Take 𝑔= 10 m s-2 )

Q24.A microscope is focused on an object at the bottom of a bucket. If liquid with refractive index 5 is poured 3 inside the bucket, then microscope have to be raised by 30 cm to focus the object again. The height of the liquid in the bucket is : (1) 75 cm (2) 50 cm (3) 18 cm (4) 12 cm

Q24.A fish rising vertically upward with a uniform velocity of 8 m s–1, observes that a bird is diving vertically downward towards the fish with the velocity of 12 m s–1. If the refractive index of water is 34 , then the actual velocity of the diving bird to pick the fish, will be __________m s−1.

Q24.A series LCR circuit is connected to an AC source of 220 V , 50 Hz. The circuit contains a resistance R = 80 Ω, an inductor of inductive reactance XL = 70 Ω, and a capacitor of capacitive reactance XC = 130 Ω . The power factor of circuit is x . The value of x is: 10

Q24.Two objects A and B are placed at 15 cm and 25 cm from the pole in front of a concave mirror having radius of curvature 40 cm . The distance between images formed by the mirror is: (1) 40 cm (2) 60 cm (3) 160 cm (4) 100 cm

Q24.A plane electromagnetic wave of frequency 20 MHz propagates in free space along x-direction. At a particular → → space and time E = 6. 6ˆj V m−1 . What is B at this point? (1) 2. 2 × 10−8ˆkT (2) −2. 2 × 10−8ˆiT (3) −2. 2 × 10−8ˆkT (4) 2. 2 × 10−8ˆi T

Q25.As shown in the figure, in Young's double slit experiment, a thin plate of thickness t = 10 μm and refractive index μ = 1. 2 is inserted infront of slit S1 . The experiment is conducted in air ( μ = 1 ) and uses a monochromatic light of wavelength λ = 500 nm. Due to the insertion of the plate, central maxima is shifted by a distance of xβ0 . β0 is the fringe-width before the insertion of the plate. The value of the x is ______.

Q25.An electron revolves around an infinite cylindrical wire having uniform linear charge density 2 × 10-8 C m-1 in circular path under the influence of attractive electrostatic field as shown in the figure. The velocity of electron with which it is revolving is ______________ × 106 m s-1. Given mass of electron = 9 × 10-31 kg

Q25.The threshold wavelength for photoelectric emission from a material is 5500 A . Photoelectrons will be emitted, when this material is illuminated with monochromatic radiation from a A. 75 W infra-red lamp B. 10 W infra-red lamp C. 75 W ultra-violet lamp D. 10 W ultra-violet lamp Choose the correct answer from the options given below : (1) B and C only (2) A and D only (3) C only (4) C and D only

Q25.In the given figure the total charge stored in the combination of capacitors is 100 µC. The value of ‘ x’ is ______________.

Q25.Match List I and List II → → A Gauss’s Law in Electrostatics I ∮ E ⋅ dl = −dϕBdt → → B Faraday's Law II ∮ B ⋅d A = 0 → → C Gauss’s Law in Magnetism III ∮ B ⋅d l = μ0ic + μ0 ∈0 dϕEdt q D Ampere-Maxwell Law IV ∮→E ⋅d→s= ∈0 Choose the correct answer from the options given below : (1) A-IV, B-I, C-II, D-III (2) A-I, B-II, C-III, D-IV (3) A-III, B-IV, C-I, D-II (4) A-II, B-III, C-IV, D-I JEE Main 2023 (25 Jan Shift 2) JEE Main Previous Year Paper

Q25.A block of mass 2 kg is attached with two identical springs of spring constant 20 N m-1 each. The block is placed on a frictionless surface and the ends of the springs are attached to rigid supports (see figure). When the mass is displaced from its equilibrium position, it executes a simple harmonic motion. The time period of oscillation is 𝜋 in SI unit. The value of 𝑋 is______. √𝑋 JEE Main 2023 (24 Jan Shift 1) JEE Main Previous Year Paper 𝑞

Q25.In the following circuit, the magnitude of current 𝐼1, is ______ A. JEE Main 2023 (30 Jan Shift 1) JEE Main Previous Year Paper - 1 A s-1, then the value of 𝑉AB at this instant will be ______ V.

Q25.Two light waves of wavelengths 800 and 600 nm are used in Young's double slit experiment to obtain interference fringes on a screen placed 7 m away from plane of slits. If the two slits are separated by 0. 35 mm , then shortest distance from the central bright maximum to the point where the bright fringes of the two wavelength coincide will be ______ mm.

Q25.In Young's double slits experiment, the position of 5th bright fringe from the central maximum is 5 cm . The distance between slits and screen is 1 m and wavelength of used monochromatic light is 600 nm . The separation between the slits is: (1) 60 μm (2) 48 μm (3) 12 μm (4) 36 μm

Q25.A point source of 100 W emits light with 5% efficiency. At a distance of 5 m from the source, the intensity produced by the electric field component is: (1) 1 W (2) 1 W 2π m2 40π m2 1 (3) 10π m2 W (4) 201 m2W

Q25.Three concentric spherical metallic shells 𝑋, 𝑌 and 𝑍 of radius 𝑎, 𝑏 and 𝑐 respectively 𝑎< 𝑏< 𝑐 have surface charge densities 𝜎, – 𝜎 and 𝜎, respectively. The shells 𝑋 and 𝑍 are at same potential. If the radii of 𝑋 & 𝑌 are 2 cm and 3 cm, respectively. The radius of shell 𝑍 is _____cm. Q26.10 resistors each of resistance 10 Ω can be connected in such as to get maximum and minimum equivalent resistance. The ratio of maximum and minimum equivalent resistance will be________.

Q25.In the figure given below. a block of mass 𝑀= 490 g placed on a frictionless table is connected with two springs having same spring constant (𝐾= 2 N m-1). If the block is horizontally displaced through 𝑋 m then the number of complete oscillations it will make in 14𝜋 seconds will be ______.

Q25.Two vertical parallel mirrors A and B are separated by 10 cm. A point object O is placed at a distance of 2 cm from mirror A. The distance of the second nearest image behind mirror A from the mirror A is _______ cm.

Q25.Unpolarised light is incident on the boundary between two dielectric media, whose dielectric constants are 2. 8 (medium – 1) and 6. 8 (medium – 2), respectively. To satisfy the condition, so that the reflected and refracted 1 rays are perpendicular to each other, the angle of incidence should be tan−1 (1 + 10θ ) 2 , the value of θ is ______. (Given for dielectric media, μr = 1 )

Q25.The difference between threshold wavelengths for two metal surfaces A and B having work function ϕA = 9 eV and ϕB = 4. 5 eV in nm is: {Given, hc = 1242 eV nm } (1) 540 (2) 276 (3) 264 (4) 138

Q25.A 2 meter long scale with least count of 0. 2 cm is used to measure the locations of objects on an optical bench. While measuring the focal length of a convex lens, the object pin and the convex lens are placed at 80 cm mark and 1 m mark, respectively. The image of the object pin on the other side of lens coincides with image pin that is kept at 180 cm mark. The % error in the estimation of focal length is: JEE Main 2023 (06 Apr Shift 2) JEE Main Previous Year Paper (1) 0. 85 (2) 1. 70 (3) 1. 02 (4) 0. 51

Q25.A person driving car at a constant speed of 15 m s-1 is approaching a vertical wall. The person notices a change of 40 Hz in the frequency of his car’s horn upon reflection from the wall. The frequency of horn is _______Hz . (Given: Speed of sound: 30 m s-1)

Q25.A convex lens of refractive index 1. 5 and focal length 18 cm in air is immersed in water. The change in focal length of the lens will be_____ cm. (Given refractive index of water = 43 )

Q25.The equation of wave is given by 𝑌= 10-2sin2𝜋160𝑡- 0 . 5𝑥+ 4, where 𝑥 and 𝑌 are in 𝑚 and 𝑡 in 𝑠. The speed of the wave is _______ km h-1.